1. Field of Invention
The present invention relates to a driving apparatus and a stop position detection method.
This application claims priority to and the benefit of Japanese Patent Application No. 2011-124249, filed on Jun. 2, 2011, the disclosure of which are incorporated by reference herein.
2. Description of Related Art
As a brushless motor in which a rotor has a permanent magnet, there is a brushless motor in which driving control is performed in position-sensorless without a position sensor for detecting a position (angle) of the rotor. In this case, the position of the rotor is detected from an edge interval of a pulse signal obtained by inputting an induced voltage, which appears at a motor terminal of an open section (non-energized phase), and an equivalent neutral-point potential to a comparator. Incidentally, there is a possibility that a signal sufficient for detecting the position of the rotor is not obtained because the induced voltage is not generated or is very low when the number of rotations is zero or very small such as when driving of the brushless motor is started.
Therefore, when voltages are sequentially applied to coils of each phase, a stop position of the rotor is detected based on a difference between rising times of currents flowing through the coils of each phase (for example, Japanese Patent Application Publication No. 2009-071926).
However, in technology disclosed in Japanese Patent Application Publication No. 2009-071926, there is a possibility that a large current flows through the coil if magnetic saturation occurs when the voltage is applied to coil of each phase. In this case, there is a possibility that, due to a load on a power supply apparatus such as a storage battery that supplies power to the motor, the stability of the power supply apparatus is impaired such as a voltage of power to be supplied by the power supply apparatus is temporarily reduced.